During the course of a surgical procedure, it is often required to displace or restrain a body tissue. This tends to facilitate surgical access to the target anatomic tissue in need of the surgical intervention, which is contained in the displaced or restrained body tissue. Alternatively, a body tissue may be displaced or restrained away from the site of a surgical intervention in which the target anatomic tissue is situated.
During many types of surgical interventions, it is also often required to constrict or ligate, either partially or fully, an anatomic conduit in order to restrict or prevent flow through said anatomic conduit, during at least a duration of the surgical intervention. For instance, during a beating heart bypass surgery procedure, an anatomic conduit such as for example a target coronary artery may be ligated to temporarily restrict or arrest blood flow through an arteriotomy incision in said target artery, while the patient's heart continues to beat. This tends to achieve a substantially bloodless surgical field during a coronary artery anastomosis surgery performed on said target artery. Other anatomic conduits include such conduits as arteries, veins, organ ducts, air passageways, or other like anatomic conduits.
Constriction or ligation of an anatomic conduit may be achieved through a hemostat or other like surgical clamp. When fragile anatomic conduits are involved, such a method of constriction or ligation tends to be traumatic. If a surgical intervention is intended on an anatomic conduit, in a region of close proximity to the site of constriction or ligation, such a method tends to yield a non-ergonomic surgical site due to the space occupied by the hemostat, or other like surgical clamp.
A non-elastic surgical suture may also be used to encircle and subsequently constrict an anatomic conduit. Pulling the loose ends of the surgical suture induces a tension in the surgical suture and results in a compressive load applied to said conduit. As such, the desired amount of constriction or ligation of anatomic conduit is achieved. The non-elastic nature of a surgical suture, and its generally thin cross-section relative to the anatomic conduit, tends to induce trauma to the said conduit. Trauma may at times result from the snaring effect, or wire-cutting effect, especially when complete ligation of an anatomic conduit is desired. Surgical sutures are generally configured with a needle at one end thereof, to facilitate their insertion through a body tissue within which an anatomic conduit is found.
Elastic ligatures have also been employed to constrict or ligate, partially or fully, anatomic conduits. The elastic quality of these elastomeric surgical loops is desirable since a certain amount of yield is provided in such surgical loops when they are engaged with anatomic tissue and pulled with the aim of ligating. As such, unlike non-elastic surgical sutures, the amount of pressure applied to an anatomic tissue, or the compression by which an anatomic conduit is constricted, tends to be more controlled. Moreover, relative to non-elastic sutures, elastomeric surgical loops will yield a certain amount if an anatomic tissue is inadvertently displaced during a surgical procedure, or will yield a certain amount if an anatomic tissue is moving or pulsating due to a physiologic function. As such, relative to non-elastic surgical sutures, there is a lower likelihood of inducing trauma to the anatomic tissue.
In certain surgeries, substantially flat elastic ligatures with solid cross section have also been employed. However, these elastic ligatures tend to dig into a body tissue or anatomic conduit if they become twisted during their deployment. This may lead to unwanted tissue trauma.
Hollow elastic surgical loops or ligatures have also been developed. With respect to solid elastic surgical loops, a hollow configuration tends to enhance the yielding potential of a surgical loop when said loop is engaged with anatomic tissue and pulled with the aim of ligating. This enhanced yielding potential tends to be accomplished without reducing the contact width of the surgical loop when it is engaged with an anatomic conduit.
Hollow elastic loops with sealed ends have also been developed with the aim of reducing the likelihood of a surgical loop twisting during its engagement and deployment with anatomic tissue. Since the ends of these hollow elastic loops are sealed to entrap air therein, collapsing of the surgical loop tends to be resisted when it is placed in contact with anatomic tissue. As such, the interior surface of the surgical loop does not easily come into contact with itself, thereby tending to reduce the likelihood of twisting said surgical loop during its deployment. Instead, this entrapped air cavity tends to facilitate the rolling of a surgical loop about its longitudinal axis as it engages with anatomic tissue. One such elastic hollow surgical loop with sealed ends is available from Quest Medical, Inc. of Allen, Tex., under brand name “Retract-O-Tape™”. The Retract-O-Tape surgical loop, or vascular loop, is configured with a needle at one end thereof to facilitate its insertion through a body tissue.
The retraction of an anatomic tissue, or the constriction of a vessel contained within an anatomic tissue, is accomplished by piercing the anatomic tissue with the needle at the end of a surgical loop or suture, threading a length of surgical loop or suture through the pierced tissue, and pulling simultaneously on both resulting lengths of surgical loop or suture; that is, the length between the pierced tissue and the free end of the surgical loop or suture, and the length between the pierced tissue and the needle-bearing end of the surgical loop or suture. Once a vessel is encircled with a surgical loop or suture, pulling the two resulting lengths in a generally opposed direction induces a compressive load on the vessel contained therein. Desired vessel constriction or ligation is achieved by maintaining the tension on each of the two free lengths of the surgical loop or suture through a variety of methods. In one method, the free lengths may be held under tension by a surgical assistant. This method represents an inefficient use of the surgical assistant's time and tends to be cumbersome and non-ergonomic for the surgeon. In another method, each of the free lengths of a surgical loop may be secured to a surgical retractor, to a surgical drape, or to another part of the patient's anatomy with a surgical clamp or other like means. This tends to compromise the ergonomics of the surgical window, and the surgeon's access thereto. The situation is further aggravated when multiple surgical loops or sutures need to be secured in this manner to achieve the desired anatomic tissue retraction or vessel constriction.
Recently, with the advent of less-invasive cardiac surgery, surgical loops have been utilized to constrict or ligate coronary arteries during the course of such surgeries. For instance, in coronary artery bypass graft (CABG) surgery performed directly on a beating heart without cardio-pulmonary assistance, elastic surgical loops may be used during at least a duration of the surgical procedure to constrict or ligate a target coronary artery requiring a bypass graft. A surgical loop is generally placed around a target coronary artery, at a location upstream of the intended arteriotomy and subsequent anastomosis, thereby serving to restrict blood flow through said target artery. Another such surgical loop may be placed at a location downstream of said arteriotomy incision, tending to minimize backflow from collateral arteries. As a result, an arteriotomy and subsequent anastomosis may be performed on said target artery in a substantially bloodless surgical field while the patient's heart continues to beat.
Surgical loops may be secured in a manner as described above or may also be secured to a coronary artery stabilizer utilized to locally immobilize a portion of the beating heart surface, in the vicinity of the target coronary artery. One such coronary artery stabilizer and method of securing a surgical loop thereto is described in International Application No. PCT/CA98/00821 by Cartier and Paolitto filed Aug. 27, 1998 and entitled “Sternum Retractor for Stabilizing the Beating Heart During Coronary Artery Bypass Graft Surgery”. Although, different types of coronary stabilizers exist, they tend to generally contact the surface of a beating heart with a substantially planar tissue-contact surface. Such tissue-contact surfaces are typically interrupted to define an arterial window serving to expose a target artery therebetween. For instance, in one example, the coronary stabilizer may have a substantially u-shaped contact surface. In another example, the coronary stabilizer may be comprised of two, or more, mating and demountable parts which form a substantially rectangular contact surface within which is disposed a substantially rectangular arterial window. In some types of coronary stabilizers, a surgical loop may be secured to said stabilizer through a feature such as a slotted attachment fitting, or other like means. Such attachment fittings generally protrude above the tissue-contact surface of the coronary stabilizer, and as such, a surgical loop is generally secured to said stabilizer in a location situated in height above the tissue-contact surface of said stabilizer. Encircling of the target artery with a surgical loop, and subsequently pulling and securing the ends of said surgical loop while applying a compressive force on the target artery, will tend to at least partially constrict the target artery, but also will tend to extrude through the arterial window, the portion of the myocardium tissue containing the encircled target artery. Generally in this configuration, the greater the extrusion of the myocardium through the arterial window, the greater the magnitude of the resulting constriction of the target artery contained substantially therein. In certain instances, this may lead to trauma of the coronary artery by virtue of extensive external snaring.
In a sense, encircling of an anatomic conduit with a surgical loop and subsequently pulling in a generally opposed direction, on each of the two resulting lengths of said surgical loop, applies a tourniquet effect to said conduit. In order to obtain a substantially 360 degree tourniquet, the surgical loop forms a helical winding around said conduit. As such, a shearing load is applied to the anatomic conduit by virtue of this helical winding, and by virtue of pulling on each of the two resulting lengths of surgical loop at different locations along the longitudinal axis of said conduit. This shearing action may induce a trauma to the anatomic conduit as it may cause it to twist and assume a tortuous configuration. This is especially prevalent with smaller diameter anatomic conduits, whose size approach the external cross-sectional dimension of the surgical loop.